This paper examines previous studies on the use and acquisition of speech acts by second language learners in order to identify issues that are yet to be investigated. The paper begins with a brief overview of the theoretical background for L2 speech act theory. Then, factors that affect native speakers’ choice of expressions are explained and the extent to which they are investigated in L2 pragmatic studies is considered. Thirdly, the strengths and weaknesses of methodology employed are discussed. In addition, this paper examines what types of speech acts that have or have not been extensively studies, focusing on Japanese as a second language. Based on these analyses, we will attempt to identify future area of studies that can deepen the understanding of the acquisition of Japanese speech acts by non-native speakers and enhance the instruction of speech acts.